Reference Clock Rate Detection for Variable Rate Transceiver Modules

Abstract

A system and method are provided for determining an optical signal frequency range in an optical / electrical transceiver. The method receives an optical receive signal having a non-predetermined data rate via a network interface, and also receives an electrical reference clock signal having a non-predetermined frequency via a framer interface. The reference clock signal frequency is cross-referenced to an optical receive signal frequency. In one aspect a clock and data recovery (CDR) voltage controlled oscillator (VCO) is selected having an output frequency matching the cross-referenced optical receive signal frequency. The optical receive signal is converted to an electrical receive signal. Initially, the VCO is frequency-locked to the reference clock. Subsequent to frequency-locking the VCO output frequency, the converted optical signal is phase-locked, generating a receive data clock. The CDR supplies a converted optical receive signal and receive data clock to the framer interface.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention generally relates to digital communications and, more particularly, to a system and method for clock rate detection in clock and data recovery (CDR) and clock synthesis units (CSUs).[0003]2. Description of the Related Art[0004]Conventionally, system platforms provide an optical transceiver module with a reference clock and data at the reference clock multiplied rate. These rates are a selection of more than half a dozen rates which continue to increase as technology moves forward. The module is required to operate at the given data rate without any system setup communication. If this setup communication protocol was provided and all modules and systems spoke this protocol, then data rate acquisition would be relatively easy. However, this is not the case, as modules and system platforms do not communicate, data rate information between each other.[0005]Some prior art CDR and CSUs optical interface data ra...

AI Technical Summary

Benefits of technology

[0009]A single module type with multiple data rate capability does not have to be preset to function at a fixed rate port configuration. Such a module is pluggable in all port configurations of different data rates. Since the module determines the correct port data rate, port compatibility and seamless operation are provided, while eliminating human intervention for system configuration and hardware logistics.

Problems solved by technology

However, this is not the case, as modules and system platforms do not communicate, data rate information between each other.

One undesirable alternative is a system platform that provides a single data rate that is not standardized among all platform developers and module vendors.

However, this capability would add to the cost and complexity of the units.

However, as mentioned above, no protocol exists for communications between CDR / CSU transceiver and a system platform.

Alternately, a CDR or CSU may be used without a reference clock, but such units are likely to provide a poor level of performance.

As another alternative, a wide band single VCO could be used that can be tuned to operate at any possible data rate, but again, the level of performance is likely to be poor.

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